The main reason [we do not forgive others is] because we don't want to. You might not want to forgive because you want to see them suffer for what they did. You might not want to forgive because you want them to feel the same hurt that they made us to feel. You might not want to forgive because you want to give them the message that if they hurt me then they will feel pain also, so they better think twice about hurting me again. You might not want to forgive because you are angry or frustrated. You might not want to forgive because you want revenge. You might not want to forgive because you enjoy playing the victim. You might not want to forgive because you really don't like that person and you want to keep it that way.